Physics Letters B607, 123-130 (2005)
Maximal CP Violation Hypothesis
and Phase Convention of the CKM Matrix
The maximal CP violation hypothesis depends on the phase
convention of the Cabibbo-Kobayashi-Maskawa matrix.
A phase convention which leads to successful prediction
under the maximal CP violation hypothesis is searched,
and thereby, possible structures of the quark mass matrices
are speculated.
US-04-09 (US-04-08 was wong number)
To appear in the proceedings of ICHEP 2004
Neutrino Masses Without Seesaw Mechanism
in a SUSY SU(5) Model With Additional $\overline{5}'_L+5'_L$
A radiatively-induced neutrino mass matrix with a simple
structure is proposed on the basis of an SU(5) SUSY GUT model
with $R$-parity violation. The model has matter fields
$\overline{5}'_{L}+5'_{L}$ in addition to the ordinary matter
fields $\overline{5}_{L}+10_{L}$ and Higgs fields
$H_u+\overline{H}_d$. The $R$-parity violating terms are
given by $\overline{5}_{L} \overline{5}_{L} 10_{L}$,
while the Yukawa interactions are given by $\overline{H}_d
\overline{5}'_{L} 10_{L}$. Since the matter fields
$\overline{5}'_L$ and $\overline{5}_L$ are different from
each other at the unification scale, the $R$-parity violation
effects at a low energy scale appear only through the
$\overline{5}'_L \leftrightarrow \overline{5}_{L}$ mixings.
In order to make this $R$-parity violation effect harmless
for proton decay, a discrete symmetry Z$_3$ and a triplet-doublet
splitting mechanism analogous to the Higgs sector are assumed.
To appear in the proceedings of YITP meeting 2004
Comments on a Flavor Symmetry
Without assuming any specific flavor symmetry and/or
any specific mass matrix forms, it is demonstrated that
if a flavor symmetry (a discrete symmetry, a U(1) symmetry,
and so on) exists, we can never obtain the observed CKM
quark mixing matrix and MNS lepton mixing matrix, even if
we can obtain reasonable mass spectra under the symmetry.
It is also discussed how to evade this trouble.
Neutrino Masses Without Seesaw Mechanism
in a SUSY SU(5) Model with Additional
$\bar{5}'_L+5'_L$
A radiatively-induced neutrino mass matrix with a simple
structure is proposed on the basis of an SU(5) SUSY GUT model
with $R$-parity violation. The model has matter fields
$\overline{5}'_{L}+5'_{L}$ in addition to the ordinary matter
fields $\overline{5}_{L}+10_{L}$ and Higgs fields
$H_u+\overline{H}_d$. The $R$-parity violating terms are
given by $\overline{5}_{L} \overline{5}_{L} 10_{L}$,
while the Yukawa interactions are given by $\overline{H}_d
\overline{5}'_{L} 10_{L}$. Since the matter fields
$\overline{5}'_L$ and $\overline{5}_L$ are different from
each other at the unification scale, the $R$-parity violation
effects at a low energy scale appear only through the
$\overline{5}'_L \leftrightarrow \overline{5}_{L}$ mixings.
In order to make this $R$-parity violation effect harmless
for proton decay, a discrete symmetry Z$_3$ and a triplet-doublet
splitting mechanism analogous to that in the 5-plet Higgs
fields are assumed.
Physical Review D71, 016010-1 -- 013010-6 (2005)
What Happens If an Unbroken Flavor Symmetry Exists?
Without assuming any specific flavor symmetry and/or
any specific mass matrix forms, it is demonstrated that
if a flavor symmetry (a discrete symmetry, a U(1) symmetry,
and so on) exists, we cannot obtain the CKM quark mixing matrix
$V$ and the MNS lepton mixing matrix $U$ except for those
between two families for the case with the completely undegenerated
fermion masses, so that we can never give the observed CKM
and MNS mixings. Only in the limit of $m_{\nu 1} =m_{\nu 2}$
($m_d=m_s$), we can obtain three family mixing with an
interesting constraint $U_{e3}=0$ ($V_{ub}=0$).
Physics Letters B574, 469-475(2004)
Neutrino Masses Without Seesaw Mechanism
in a SUSY SU(5) Model with Additional \bar{5}'_L + 5'_L
Within the framework of an SU(5) SUSY GUT model, a possible
general form of the neutrino mass matrix induced by
R-parity violation is investigated. The model has matter
fields \overline{5}'_{L}+5'_{L} in addition to the ordinary
matter fields \overline{5}_{L}+10_{L} and Higgs fields
H_u+\overline{H}_d. The R-parity violating terms are
given by \overline{5}_{L} \overline{5}_{L} 10_{L}, while
the Yukawa interactions are given by \overline{H}_d
\overline{5}'_{L} 10_{L}. Since the matter fields
\overline{5}'_L and \overline{5}_L are different from
each other at the unification scale, the R-parity violation
effects at a low energy scale appear only through the
\overline{5}'_L \leftrightarrow \overline{5}_{L} mixings.
In order to make this R-parity violation effect harmless
for proton decay, a discrete symmetry Z_3 and a triplet-doublet
splitting mechanism analogous to that in the 5-plet Higgs
fields are assumed.